High-strength,centrifugally cast copper-base alloy bearing cage

ABSTRACT

ALLOYS CONSISTING ESSENTIALLY OF FROM ABOUT 26.0 TO ABOUT 34.0% ZINC, FROM ABOUT 4.5 TO ABOUT 10.0% (PREFERABLY FROM ABOUT 4.5 TO ABOUT 6.0%) MANGANESE, FROM ABOUT .0.5 TO ABOUT 1.5% IRON, FROM ABOUT 1.0 TO ABOUT 2.5 ALUMINUM, AND THE BALANCE COOPPR. LEAD CAN BE OPTIONALLY ADDED, IN AMOUNT OF FROM ABOUT 0.5 TO ABOUT 1.5%. THE ALLOYS HAVE IMPROVED PHYSICAL PROPERTIES, PARTICULARLY AT ELEVATED TEMPERATURES, AND CAN BE CENTRIFUGALLY CAST FOR MANUFACTURE INA NTIFRICTION BEARING CAGES.

April 24, 1973 w. D. BROWN ETAL HIGH-STRENGTH,

CENTRIFUGALLY CAST COPPER-BASB ALLOY BEARING CAGE Filed Dec. 11, 1970 wS Ca H n R SM 0 A TNR N E EW O w W O MSR AAE UMN L M M WT G VI BATTORNEYS United States Patent Office 3,729,347 Patented Apr. 24, 1973ABSTRACT OF THE DISCLOSURE Alloys consisting essentially of from about26.0 to about 34.0% zinc, from about 4.5 to about 10.0% (preferably fromabout 4.5 to about 6.0%) manganese, from about 0.5 to about 1.5% iron,from about 1.0 to about 2.5 aluminum, and the balance copper. Lead canbe optionally added, in amount of from about 0.5 to about 1.5%. Thealloys have improved physical properties, particularly at elevatedtemperatures, and can be centrif ugally cast for manufacture inantifriction bearing cages.

BACKGROUND OF THE INVENTION For decades, it has been the practice tomanufacture cages for ball or roller bearings from an alloy known asAlcop. This alloy has a nominal composition of 63% copper, 35% zinc, 1%aluminum, and 1% lead.

Alcop was developed in the 1930s to combat a rash of bearing cagefailures which occurred at that time, when it was conventional tomanufacture the cages from red brass containing 85% copper, 5% tin, 5%lead, and 5% zinc.

Alcop was very successful in overcoming the problems of the day, andover the years became a very popular material for antifriction bearingcages. As minimum physical properties, Alcop has a yield tensilestrength of 25,000 p.s.i., an ultimate tensile strength of 65,000p.s.i., a Rockwell hardness of 55 on the b scale, and 25% elongation ina 2" gauge length.

As the years went by, however, bearing service applications became moresevere and a need developed for bearing cage alloys having increasedstrength, particularly at high temperatures, and having extended servicelife. A main object of the invention is the fulfillment of this need.

There are a number of known expedients for strengthening copper-basealloys. However, attempts to apply such expedients to the strengtheningof Alcop have encountered complicating factors. One of such factorsappeared in the bearing cage manufacturing process.

In the manufacturing of bearing cages, one of which is generallyindicated at in the drawing, it is common practice to firstcentrifugally cast a hollow cylinder and then cut transverse slices fromthe cylinder at closely spaced locations along the longitudinal axis ofthe cylinder to produce a plurality of rings, as 12. Each ring is thenmachined at spaced locations around its periphery to form apertures, as14, which receive the individual balls or rollers of the bearing. Thereare many, many variants which can be practiced within the framework ofthis basic procedure, but the essentials of the process remain the same.

The centrifugal casting of the cylinders is a delicate operation. Eachcylinder is cast in a permanent, cylindrical, mold or die which isdisposed with its longitudinal axis in horizontal or verticalorientation and which is rotated at high speeds around the axis whilemolten metal is introduced into one end of the die. The die size andspeed of rotation, desired cylinder wall thickness, G- forces on themolten metal, and other factors, all must be carefully interrelated tosuccessfully produce sound castings. One of the reasons that Alcop wasso successful is that it lent itself well to this process. Attempts tochange the chemistryof Alcop encountered difiiculties in the cylindercasting procedure. The cast cylinders tended to be unsound because ofcracks formed during the centrifugal casting process.

Accordingly, another object of the invention is the provision ofimproved and strengthened copper-base alloys and bearing cages which canbe successfully centrifugally cast.

Other objects and advantages of the invention will appear to thoseskilled in the art from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS The sole figure, to which referencehas already been made, is a perspective view of a bearing cage for aball bearing.

DETAILED DESCRIPTION It has been found that copper-base alloyscontaining particular amounts of zinc, manganese, iron and aluminum havethe necessary improved strength properties for hearing cages subjectedto severe present-day service conditions, while being susceptible ofsuccessful centrifugal casting. The alloys have improvedroom-temperature yield tensile strength, ultimate tensile strength,fatigue strength, and hardness, and moreover, retain good ductility.Further, the allo'ys have surprising elevated-temperature properties,which are important because in present-day technology many bearings mustoperate successfully at elevated temperatures.

Alloys in accordance with the invention consist essentially of fromabout 26.0 to about 34.0% zinc, from about 4.5 to about 10.0%(preferably from about 4.5% to about 6.0%) manganese, from about 0.5 toabout 1.5% iron, from about 1.0 toabout 2.5% aluminum, and the balancecopper. The alloys can also contain from about 0.5 to about 1.5% lead asan optional additive where increased machinability is desired. As usedherein, the phrase consisting essentially of embraces materials, e.g.,impurities and diluents, which do not materially affect the basicproperties of the composition. All composition percentages herein are byweight.

Alloys in accordance with the invention are characterized by a minimumroom-temperature yield tensile strength of about 32,000 p.s.i., anincrease of about 28% over Alcop. The minimum room-temperature ultimatetensile strength is about 70,000 p.s.i., an increase of about 8% fromAlcop. The minimum room temperature Rockwell b hardness is 75, up about36% over Alcop. Fatigue strength is improved, as are stress-ruptureproperties. Ductility is good. The strength properties of the alloys canbe still further improved by heat treatment. The allo'ys exhibit amartensitic type of structure after solution treating and quenching. Thealloys can be cast into cylinders for manufacture of bearing cages inaccordance with conventional procedures.

The foregoing properties are very much sought after and highlydesirable, but it is in respect to elevatedtemperature properties thatoutstanding results are obtained. The alloys have excellent strength andhardness stability, at elevated temperatures, and this is very importantbecause many bearings are subject to such temperatures in service.

The manganese content is important. Alloys having manganese contentsbelow the range specified have insufficient strength. Further, alloyswith the low manganese tend not to respond to heat treatment. Alloyscontaining more manganese than the preferred range of from about 4.5 toabout 6.0% are difficult to centrifugally cast with success. Closecontrol over the speed of rotaappended claims.

Zn Mn Fe Al Pb Cu Exam lo:

The alloy of Example I has the following room-temperature properties: ARockwell b hardness of 75; a yield tensile strength of 32,000 p.s.i.; anultimate tensile strength of 70,000 p.s.i.; and 35% elongation in 2". Infatigue, the alloy can withstand over 6.8 million cycles of fluctuationbetween 40,000 and 4,000 p.s.i. axial tension. When notched, the fatiguelife is over 4.1 million cycles of fluctuation between 25,000 and 2,500p.s.i. tenslon.

At 450 F., the alloy of Example I has a yield tensile strength of 30,200p.s.i. and an ultimate tensile strength of 54,000 p.s.i. The alloy notonly retains a Rockwell b hardness of 75 after 20.5 hours at 450 F., butalso actually increases in hardness to 78.5 Rockwell b after 138.5 hoursat 450 F. In stress-rupture, the alloy can withstand a stress of 29,000p.s.i. at 450 F. for 100 hours. Such stress is about 96% of the yieldstrength at that temperature, and it is surprising that the alloy hassuch elevated-temperature strength.

At room temperature, the alloy of Example II has the followingproperties: a Rockwell b hardness of 79; a yield tensile strength of33,000 p.s.i.; an ultimate tensile strength of 80,000 p.s.i.; a fatiguestrength of 39,000 p.s.i.; and 34% elongation in 2". At 450 F., theyield tensile strength is 32,000 p.s.i. and the ultimate tensilestrength is 55,000 p.s.i. In stress-rupture, the alloy surprisingly canwithstand 30,000 p.s.i. (94% of the yield strength) for 100 hours at 450F.

At room temperature, the alloy of Example III has a Rockwell b hardnessof 85, a yield tensile strength of 52,000 p.s.i., an ultimate tensilestrength of 95,000 p.s.i., and a fatigue strength of 30,000 p.s.i. At450 F., the alloy has a yield tensile strength of 52,000 p.s.i. and anultimate tensile strength of 68,000 p.s.i. In stress-rupture, the alloycan withstand 32,000 p.s.i. stress for 100 hours.

We claim:

1. A centrifugally cast antifriction bearing cage composed of an alloyconsisting essentially of from about 26.0 to about 34.0% zinc, fromabout 4.5 to about 6.0% manganese, from about 0.5 to about 1.5% iron,from about 1.0 to about 2.5% aluminum, from about 0.5 to about 1.5 lead,and the balance copper.

2. A centrifugally cast bearing cage as defined in claim 1, wherein thezinc is present in an amount of about 29%, the manganese is present inan amount of about 5.1%, the iron is present in an amount of about 0.7%,the aluminum is present in an amount of about 1.1%, the lead is presentin an amount of about 0.6% and the copper is present in an amount ofabout 63.5%

3. A centrifugally cast bearing cage as defined in claim 1, wherein thezinc is present in an amount of about 29%, the manganese is present inan amount of about 4.7%, the iron is present in an amount of about 1.1%,the aluminum is present in an amount of about 2.0%, the lead is presentin an amount of about 0.7 and the copper is present in an amount ofabout 62.5%

References Cited UNITED STATES PATENTS 1,625,777 4/1927 Kuchen 157.51,869,554 8/1932 Ellis 75157.5 3,097,093 7/1963 Fox et a1. 75-4613,544,313 12/1970 Sadoshima et al. 75-1575 2,479,596 8/1949 Anderson eta1. 75-157.5

OTHER REFERENCES Metals Handbook, vol. 1, 8th ed., 1961, pages 972- 974,1046 and 1047.

CHARLES N. LOVELL, Primary Examiner US. Cl. X.R.

